1. Field of the Invention
The invention relates generally to the field of well logging conveyance. More specifically, the invention relates to methods and devices for conveying well logging instruments through a wellbore.
2. Background Art
Electric wireline wellbore logging instruments are used for, among other things, making measurements of various physical properties of earth formations penetrated by wellbores. Electric wireline logging instruments are typically inserted into the wellbore by the force of gravity while connected to the end of an armored electrical cable, and are returned to the earth's surface by retracting the cable. For example, the cable is typically retracted by a winch or similar spooling apparatus. The cable provides electrical power to the instruments to operate the various sensors and related devices therein and provides signal communication path(s) between the various sensors and related devices and a recording unit disposed at the Earth's surface.
Certain wellbores are drilled so as to have significant inclination from vertical over at least a portion of the wellbore. Other wellbores can have a section which is substantially horizontal. Still other wellbores may be drilled through formations that are subject to swelling or caving, or having fluid pressures therein that make passage of well logging instruments past them that are unsuitable for typical well logging instrument conveyance techniques. Gravity cannot be practicably used to insert well logging instruments into these wellbores, so various methods have been devised to insert well logging instruments into such wellbores.
One of the methods known in the art for inserting well logging instruments into highly inclined or horizontal wellbores is to attach the well logging instruments to the end of a pipe comprising threaded sections (“drill pipe” or “tubing”), and to lower the pipe into the wellbore by threadedly attaching additional sections to the pipe at the upper end thereof. After the well logging instruments are inserted to a desired depth in the wellbore, an electrical cable may be attached to the upper end of the well logging instruments, typically by pumping the cable through the center of the pipe until the cable latches onto a special electrical and mechanical connector disposed at the top of the well logging instruments. The cable can be inserted into the center of the pipe from the outside of the pipe through a device called a “side entry sub.” A side entry sub is a short section of pipe having a sealable opening through a side wall of the section of pipe, which enables passage of the cable through the wall of the pipe section. The side entry sub is typically assembled to the pipe at a substantial distance below the upper end of the pipe. Assembled in this position, the side entry sub enables raising the well logging instruments within the wellbore (or withdrawing them from the wellbore) by removing sections from the pipe simultaneously with spooling of the cable as the logging instruments are raised in or withdrawn from the wellbore. By such procedure, portions of the wellbore can be measured with the well logging instrument without repeated insertion and removal of the cable from the inside of the pipe.
A drawback to using pipe to convey the well logging instruments using procedures known in the art is the presence of the cable outside the pipe from the position of the side entry sub up to the earth's surface. In some cases control of fluids which may be present in the wellbore requires using equipment located at the earth's surface designed to seal an annular space between the pipe and the wellbore. In other cases it is necessary to maintain fluid pressure on the wellbore from the earth's surface in order to obtain valid measurements from the instruments disposed in the wellbore. Cable disposed outside the pipe disturbs the operation of the sealing equipment and makes it difficult to seal the wellbore for maintaining fluid pressure.
Well logging instruments are also known in the art to be inserted into the wellbore by using a coiled tubing having a coaxially inserted electrical cable. Because the cable is coaxially inserted through the coiled tubing, it is possible to seal the annular space between the wellbore and the coiled tubing with equipment similar to that used to seal the annular space outside the sectioned pipe.
U.S. Pat. No. 5,433,276 issued to Martain et al. described a method and apparatus for inserting electric wireline logging instruments into a wellbore using an apparatus comprising pipe assembled from sections and coiled tubing having a coaxially inserted armored electrical cable (“wireline”). The method includes the steps of attaching a first part of a submersible electrical connector to one end of the coiled tubing and to the wireline inside the coiled tubing. A second part of the submersible connector is attached to one end of the wireline tools. A first part of a selectively operable latching mechanism is attached to the same end of the wireline logging instruments. A second part of the latching mechanism forms part of a latching sub which is attached to one end of the pipe. The well logging instruments are attached to the pipe by engaging the first and second parts of the latching mechanism, and the instruments are inserted into the wellbore to a predetermined depth by assembling the sections of the pipe. The coiled tubing is then inserted into the interior of the pipe until the submersible connector is engaged. The latching mechanism is selectively operated to release the well logging instruments from the sub, and the coiled tubing is inserted further into the wellbore until the well logging instruments reach a desired depth. The coiled tubing is then withdrawn until the instruments engage the sub. The latching mechanism is then selectively operated so that the well logging instruments are attached to the sub. The coiled tubing is then withdrawn from the pipe, which disengages the submersible connector. The well logging instruments are then withdrawn from the wellbore by disassembling the sections of the pipe.
U.S. Pat. No. 4,041,780 issued to Angehrn describes a self-contained, battery powered well logging instrument that can be pumped down the interior of a drill pipe string having a catcher sub at its lower end. When the well logging instrument latches into the catcher sub, the pumped fluid circulation is blocked, after which increased pump pressure switches a valve assembly to recreate circulation and energize the well logging instrument to a “standby” position. An accelerometer in the well logging instrument detects the upward movement of the well logging instrument and switches the circuitry from standby to a “record” mode. The output from a clock controlled by the downhole accelerometer is recorded along with the logging information (measurements of formation properties) measured by sensors on the well logging instrument and is synchronized with pipe footage measurements and with a similar such accelerometer and clock at the Earth's surface which are responsive to the movement of the pipe string at the Earth's surface. The recorded logging measurements are thus related to wellbore depth by correlating with the data simultaneously recorded at the Earth's surface. As an alternative embodiment, the well logging instrument is attached to the drill pipe prior to running the pipe into the wellbore.
U.S. Pat. No. 4,597,440 issued to Pottier and assigned to the assignee of the present invention describes a method for displacing a well logging instrument through a non-gravity descent portion of a wellbore such as a highly deviated portion. The disclosed method includes assembling a well logging instrument at the lower end of a drill pipe as an exposed extension to the drill pipe, displacing the well logging instrument thus exposed through the portion of the wellbore by connecting additional sections of drill pipe and lowering the drill pipe, and, during this displacing, continuously generating and sending uphole a signal indicative of the compressive load undergone by the well logging instrument.
U.S. Pat. No. 4,457,370 issued to Wittrisch describes a method for performing well logging or well servicing operations in a predetermined inclined or horizontal zone of a well following an initial vertical portion thereof. The method includes fastening a logging instrument or well servicing tool body at the end of a string of rods (such as drill pipe) lowered into the wellbore. The tool body includes an electrical connector. The method includes lowering, at the end of an electrical cable, from the Earth's surface, a mating connector adapted to fit the connector on the wellbore tool. Coupling the connectors is performed by the action of a force generated at least partly by the pressure of a fluid pumped through the pipe string, and supplying electric power through the cable and the joined connectors to the well logging or servicing tool for its operation in the predetermined zone.
U.S. Pat. No. 6,578,631 issued to Milne et al. describes a method of well logging in which the well logging instrument is delivered to the bottom of the well within a drill pipe and then the well is logged by withdrawing the drill pipe with the sensor portion of the well logging instrument protruding from the drill pipe. Following the logging operation, the well logging instrument is returned to the surface by reverse circulation.
U.S. Pat. No. 6,755,257 issued to Spencer et al. describes an apparatus and method for deploying a compact battery/memory well logging instrument for acquiring data in deviated or horizontal wellbores. A drill pipe assembly includes a drill pipe having secured at a downhole end thereof a delatching latching sub. The delatching sub contains an extendable running sub supporting a battery/memory logging instrument. The running sub occupies an initial retracted position during deployment of the drill pipe, whereby well the logging instrument is protected within one or more drill pipe stands. The running sub is movable by a messenger to a second, extended position in which its logging instrument protrudes from the end of the drill pipe. The drill pipe assembly may therefore be used to protect the well logging instrument during running in operations; and then the logging instrument is extended out the end of the drill pipe for commencement of logging operations.
U.S. Pat. No. 6,269,891 issued to Runia discloses a system for drilling and logging of a wellbore drilled through subsurface formations. The system includes a well logging instrument string and a drill string having a longitudinal channel for circulation of drilling fluid. The drill string includes a port providing fluid communication between the channel and the exterior of the drill string. The channel and the port are arranged to allow the well logging instrument string to pass through the channel and from the channel through the port to a position exterior to the drill string. The system further includes a removable closure element adapted to selectively close the port, wherein the logging instrument string may be selectively connected to the closure element.
U.S. Patent Application Publication No. 2004/0118611 filed by Runia discloses a method of drilling a wellbore into subsurface formations is-provided, including using a drill string which includes at its lower end a bottom hole assembly comprising a drill bit, a drill steering system, and a surveying system, wherein the drill string includes a passageway for an auxiliary tool to move from a first position interior of the drill string above the bottom hole assembly to a second position, wherein at least part of the auxiliary tool is exterior to the drill string below the bottom hole assembly. The passageway can be selectively closed. The method also includes drilling so as to progress the drill string into the formations until a tool operating condition is met; opening the passageway; passing an auxiliary tool from the first position through the passageway to the second position, and operating the auxiliary tool at the second position.
U.S. Pat. No. 7,134,493 issued to Runia discloses a well logging system that may be used in a wellbore. A tubular conduit extends from the Earth's surface into the wellbore and contains a body of wellbore fluid. A well logging instrument string may be passed from a position within the conduit to a position outside the conduit at a lower end part thereof, and may be suspended by the conduit in the position outside the conduit. A pressure pulse device is arranged within the conduit in a manner that the pressure pulse device is in data communication with the well logging instrument string. The pressure pulse device is capable of generating pressure pulses in the body of wellbore fluid, which pressure pulses represent data communicated by the well logging instrument string to the pressure pulse device during logging of earth formation by the well logging instrument string. The system further includes a control system in fluid communication with the body of wellbore fluid and arranged to receive the pressure pulses.
U.S. Patent Application Publication No. 2004/0238218 filed by Runia et al. discloses a method and system for introducing a fluid into a borehole, in which there is arranged a tubular drill string including a drill bit. The drill bit is provided with a passageway between the interior of the drill string and the borehole, and with a removable closure element for selectively closing the passageway in a closing position. There is further provided a fluid injection tool comprising a tool inlet and a tool outlet. A method disclosed in the '218 publication includes passing the fluid injection tool through the drill string to the closure element, and using it to remove the closure element from the closing position; passing the fluid injection tool outlet through the passageway, and introducing the fluid into the borehole from the interior of the drill string through fluid injection tool into the borehole.
There continues to be a need for well logging instrument conveyance methods and apparatus that reduce the risk of damage to the well logging instruments and increase the reliability of moving the logging instruments into and out of wellbores where wellbore conditions make instrument conveyance difficult and risky.